1. Field of the Invention
The present invention relates to an organic light emitting display (OLED), and more particularly to an organic light emitting display having color modulation layers.
2. Description of the Related Art
In general, an organic light emitting display includes a substrate, an anode located on the substrate, an emission layer (EML) located on the anode, and a cathode located on the emission layer. In such an organic light emitting display, when a voltage is applied between the anode and the cathode, holes and electrons are injected into the emission layer, the holes and the electrons injected into the emission layer are recombined to emit light.
A method of forming emission layers corresponding to red, green, and blue is used to realize a full color of the organic light emitting display. However, since the emission layers corresponding to red, green, and blue have different lifetime characteristics, it is difficult to maintain white balance when the display ages.
In order to solve the above-mentioned problem, there has been known a method of forming an emission layer emitting white light and forming color filter layers extracting light components corresponding to red, green, and blue from the white light emitted from the emission layer. For example, U.S. Pat. No. 6,515,428 to Yeh et al discloses an active matrix organic light emitting display having an emission layer for emitting white light and red, green, and blue color filters which are formed using a photolithography method. However, the color reproducibility of such an organic light emitting display depends upon intensity by wavelength of the white light emitted from the emission layer and characteristics of the color filter layers. It is known that the strength or intensity of a green component of the white light emitted from the emission layer is generally small. Thus reproducibility of the organic light emitting display employing the red, green, and blue color filters is poor.
In order to form the color filter layers using the photolithography method, a process of forming color filter layers of respective colors on the whole substrate and exposing, developing, and patterning the color filter layers needs to be repeated. A heating process needs to be performed to remove a volatile solvent contained in the layers formed using the photolithography method. In this method, there are disadvantages in that many process steps are required for forming the color filter layers using the photolithography method and that the time for fabricating an organic light emitting display is increased. Therefore, what is needed is an improved OLED that can maintain white balance even when aged and can offer improved color reproducibility, reduced fabrication time, and high resolution.